DESCRIPTION The object of this pilot study is to ascertain families with multiple members having prostate cancer (i.e. multiplex families) at less than 65 years of age. The final sample shall consist of 100 kinships; 50 families will be ascertained in the next two years. The specific aims for this study are 1) to analyze the mode of inheritance for prostate cancer in these families and 2) to evaluate the power of the sample for finding disease susceptibility genes with genetic linkage analysis. The long term goal is to search for susceptibility genes in the ascertained prostate cancer families. The etiology of prostate cancer, one of the most common cancers among males in North America, is poorly understood. Current understanding suggests that multiple genetic alterations are important in the process of this disease. A thorough screening of multiplex families with prostate cancer can provide a sample for genetic linkage analysis to find disease susceptibility genes for prostate cancer and to independently confirm results of studies having found that certain chromosomal regions might be involved in the pathogenesis of this disease. Additionally, hereditary prostate cancer can serve as a model for prostate cancer in the general population. From families willing to participate in a genetic linkage study, their pedigrees will be determined. The screening of prostate cancer patients will begin in San Antonio, Texas and its vicinity with over 50 percent Mexican American inhabitants. Thus, the sample is expected to consist of several Mexican American families. Heterogeneity of the sample might be caused by including different races or ascertaining probands with a wide range regarding age of onset. The statistical analysis will take this into consideration. It is anticipated that the results of the study will form the foundation for a systematic search of genes involved in the pathogenesis of prostate cancer by using (1) the candidate gene approach and (2) the "shot gun" approach for specific chromosomal regions of interest (i.e. testing linkage of the disease with genetic markers evenly distributed over specific chromosomal regions). This study will be the third linkage study on prostate cancer performed in the USA, it will contribute to the understanding of the etiology of prostate cancer. It will analyze a large number of kinships and provide new information on this disease in Mexican Americans, a minority group in which little is known about hereditary prostate cancer at the present time.